MILK SUGAR AND LACTIC ACID 



45 



fermentation takes place is entirely dependent upon 

 the temperature and other conditions to which the milk 

 is subjected. 



52. Determining the Acidity of Milk. — The methods 

 employed in chemical analysis for determining the 



Fio. 13. — Apparatus for te.sting acidity of milk, 



per cent of acid present in other materials are also 

 ai)plicable to milk. The lactic acid that is developed 

 in the souring of milk belongs to a general class of 

 bodies — acids - — that are capable of uniting with or 

 being neutralized by substances known as alkalies. 

 A definite amount of an acid will always require a 



